A Google spokesman confirmed the majority of Gmail users - millions of people - were affected by the 100-minute outage but refused to disclose the exact number of people who could not access the service.

Ben Treynor, vice president of Engineering, apologised to all Gmail users via the service’s blog, calling the crash a “Big Deal”, citing the failure of several routers as the cause of the problem.

As more businesses move their IT operations into 'the cloud' glitches like last night’s crash will raise doubts about the wisdom of moving data and email services online.

Tim Willey, director in consulting at Deloitte said: “The glitch shows how nascent these services still are. Gmail, and other similar cloud services, work well for consumers who receive the service free and therefore are willing to put up with problems. However for most businesses, email is service critical and I think glitches like these will make companies suspicious about moving into the cloud until there is some proof these problems are ironed out.

"Most companies typically pay for a second network on the off chance its first one goes down. When services like this run on the web, problems are to be expected.”

However, Mr Treynor said Google engineers “would be hard at work over the next few weeks” implementing Gmail reliability improvements. He added: “Gmail remains more than 99.9% available to all users, and we're committed to keeping events like today's notable for their rarity.”

Google offers all businesses which use their app suite a 24-hour telephone help line in the event of such glitches. This number is not available to the public.